Critical behavior of the specific heat in Ti-Si amorphous alloys at the metal-insulator transition

TL;DR

This study investigates the specific heat near the metal-insulator transition in amorphous Ti-Si alloys, revealing anomalous behavior linked to electron-electron interactions and comparing results with theoretical models.

Contribution

First measurement of specific heat behavior near the metal-insulator transition in amorphous Ti-Si alloys, highlighting electron-electron interactions and theoretical model comparisons.

Findings

Specific heat coefficient is temperature-independent above 2 K.

Anomalous downturn of gamma below 2 K fits a logarithmic dependence.

Results align with models involving electron-electron interactions and localization phenomena.

Abstract

In this paper, we report the measurements of specific heat of an amorphous $Ti_{9.5}Si_{90.5}$ alloy located very close to the critical point of the metal-insulator transition. In the presence of a magnetic field, the specific heat is dominated by the Schottky anomaly caused by magnetic moments associated with the dangling bonds in the matrix of amorphous Si. Subtraction of this contribution exposes the behavior of the electronic specific heat coefficient $\gamma$. The coefficient is temperature-independent above 2 K and is, in order of magnitude, close to the value expected in the absence of electron-electron interactions. In the temperature range 0.4-1.5 K, the coefficient $\gamma$ shows an anomalous downturn, which can be approximated by the dependence $\gamma\left(T\right)=\gamma_0ln{(T/T_0)}$, with $T_0\approx0.2$ K . In a companion paper, we found that the Hall coefficient in Ti-Si alloys is affected by the electron-electron interaction up to much higher temperature of 150 K and also varies critically across the metal-insulator transition. We compare our results with theoretical predictions for three models, which can potentially explain the anomalous behavior of the specific heat: generalized non-linear $\sigma$ model, Coulomb glass, and many-body localization.